More specifically, the invention relates to an adjustment mechanism for a vehicle seat, comprising a gearbox, an eccentric element driven by a driving unit, an eccentric gear wheel rotatably mounted on the eccentric element, a drive output unit equipped with an inner gear ring which cooperates with the eccentric gear wheel by partial engagement of the teeth, and a sliding block equipped with a first and a second longitudinal guide, the sliding block cooperating functionally with the eccentric gear wheel by means of the first longitudinal guide, the sliding block cooperating functionally with the gearbox by means of the second longitudinal guide.
Document EP 1 728 005 describes an example of such an adjustment mechanism in which the gearbox is made of plastic, while the sliding block is made of heat-treated metal in order to cooperate functionally with the eccentric gear wheel.
This contact between plastic and metal can have undesirable consequences. When significant stress is transmitted from the sliding block to the gearbox, for example in case of a violent impact on the vehicle, the contact between plastic and metal can cause the gearbox to break and the release of sliding block fragments.
To solve this problem, document EP 1 728 005 for example proposes the addition of a fastening flange of heat-treated metal, adapted to cooperate with the sliding block and to be attached to the plastic gearbox. This has the disadvantage, however, of requiring a supplemental part of heat-treated metal.